Impregnation of laser incised wood of Douglas fir and Japanese cedar by dipping (passive impregnation) in solutions of copper azole (CuAz-B) and a fire retardant (PPC)

Abstract

Abstract The performance of the passive impregnation method of CO2-laser incised lumber has been investigated concerning wood preservation against different wood-destroying agents. Copper azole type B (CuAz-B) preservative and polyphosphatic carbamate (PPC) fire retardant were impregnated into Douglas fir and Japanese cedar lumber under both green and kiln-dried conditions. Final drying of the lumber was performed by steam injection or kiln drying. The temperature and pressure change in the lumber, as well as the total chemical retention, penetration, decay resistance, fire retardancy and total treatment time were calculated according to different standards. The preservative retention was higher in the Japanese cedar for both green and kiln-dried conditions (5.32 and 5.58 kg m-3, respectively) compared to Douglas fir (5.01 and 4.81 kg m-3). Fire retardant retentions were more than 100 kg m-3 in all cases. The penetration was approximately 100% throughout the lumber. There were no significant differences in the decay resistance test between the different categories of lumber. Moreover, it was possible to treat the green lumber in less than 48 h starting from the green conditon to the final drying. Hence, the presented passive impregnation technique could be useful for industrial application.